This application claims the priority of 198 38 748.2, filed Aug. 26, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a fuel injection nozzle injecting onto the combustion space of an internal combustion engine. More particularly, it relates a nozzle which injects fuel onto a combustion space of an internal combustion engine, configured to be surrounded in a nozzle receptacle located on the same side as the internal combustion engine and to be open towards the combustion space, comprising a nozzle body. A nozzle neck is offset to the nozzle body. An injection orifice is arranged at an end of the neck located on a combustion-space side, and a shielding sleeve radially overlaps the nozzle neck to delimit an annular gap relative to the nozzle neck. With the nozzle in a mounting position, a radial clearance is defined relative to the surrounding nozzle receptacle. The nozzle is insertable into the nozzle receptacle in a direction of the combustion space and, with the nozzle mounted position, the shielding sleeve being axially clamped, with an annular collar provided at an end thereof facing the nozzle body, between the nozzle body and nozzle receptacle in a region of the beginning of the neck.
Fuel injection nozzles are known in many forms. German Patent Specification 873 011 shows various configurations of fuel injection nozzles in which the nozzle neck is assigned a shielding sleeve which, via an annular collar provided at its end facing the nozzle body, is braced between the nozzle body and nozzle receptacle.
Moreover, in some known embodiments, the shielding sleeve is radially braced relative to the nozzle neck on part regions of the latter. Due to the direct connection with the combustion space, the shielding sleeve, like the nozzle neck, which has al least one injection orifice on the combustion-space side, is exposed to high thermal and also mechanical loads as a result of the extreme temperature and pressure fluctuations occurring when the internal combustion engine is in operation.
Particularly when the shielding sleeve is at least partially free relative to the nozzle neck surrounded thereby and, because of the given dimensions of the gap in relation to the nozzle neck, on one hand, and to the nozzle receptacle, on the other hand, is also exposed to different load pressures according to the pressure fluctuations in the combustion space, the loads acting on the shielding sleeve can even assume extreme values. Ultimately, these values may cause fatigue fractures leading to fracturing of the shielding sleeve.
There is, therefore, the risk that a part of the shielding sleeve which is remote from the annular collar in the direction of the combustion space loses its connection with the nozzle and falls into the combustion space, especially when the shielding sleeve has a thin-walled configuration over part regions of the nozzle neck, with corresponding transitions to regions of greater wall thickness, thus, for example, in the region of the transition to the annular collar.
If parts of the shielding sleeve enter the combustion space, serious damage to the internal combustion engine usually results. This is also the case of other foreign bodies entering the combustion space, if only in view of the small free spaces available at least in the top dead center position.